The long-term objective of the Honigberg lab is to identify the mechanisms by which yeast regulate their transition into the meiotic pathway. This system presents a unique opportunity to study fundamental mechanisms by which diverse signals are integrated to control cellular fates. The first specific aim of the proposal is to determine the gene regulatory code for IME2, i.e. to identify all of the regulatory elements that control expression of this gene and the signal or signals to which they respond. This aim will be achieved through extensive mutagenesis of the promoter of a genomic ime2-lacZ allele, followed by assaying each ime2-x-lacZ mutant under all combinations of the three major signals that regulate this gene. Analysis of this combination of sequence and expression data will reveal the logic circuits underlying the gene regulatory code. The second aim of the proposal is to identify interactions between IME2 regulatory elements. The first part of this aim will be accomplished by measuring the effect of selected ime2-x-lacZ alleles on association of Ime1p and Rpd3p with the URS1 regulatory element of IME2. The second part of this aim will be to determine the interactions between IME2 regulatory elements that have shared functions. This will be accomplished by epistasis (double mutant analysis). Because the proposed research will result in the first complete description of a eukaryotic gene regulatory code, accomplishing this project provides a framework for understanding regulatory codes in other genes, including genes whose altered expression results in human disease. Defects in the regulation of transcription have profound effects on human health, affecting such diverse diseases as diabetes, cancer, and Parkinson's. Because the mechanism of transcriptional regulation is complex and still poorly understood, studying transcriptional regulation in a model genetic organism, the budding yeast S. cerevisiae, can lead to fundamental discoveries that advance our understanding of the etiology of these diseases.